Golden Opportunities

All that glisters is not gold, oft have you heard it told ~ William Shakespeare, The Merchant of Venice True, but there’s still gold in them there hills – and elsewhere. At prices today, mines long believed played out are being revived near and far. When gold reached $1,063 an ounce Toronto-based Romarco Minerals Inc. reopened the historic Halle Gold Mine near Kershaw, South Carolina, the only gold mine east of the Mississippi.

But why dig deep into the Earth’s crust to extract the precious metal when plants can do it for you? Mustard plants, wheat, alfalfa, oats, are all but some examples that are known to be able to concentrate minute traces absorbed from gold-rich soils. The process is called phytoremediation or phytomining. Almost a decade ago, no less a publication than the National Geographic magazine reported that Rumpelstiltskin, the fairy tale rogue who spun straw into gold, had nothing on two University of Texas researchers. Miguel Yacaman and Jorge Gradea-Torresdey reportedly had developed a way of extracting gold from oats. The trick revolved around a suitable solvent to recover the gold from the ashes of the absorbing grain.

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Even earlier, in October 1998, the highly respected scientific journal Nature reported on the success of researchers in New Zealand on using mustard plants, Brassica juncea, to extract gold from soil. Robert Brooks and Chris Anderson, who headed the team from Massey University in Palmerston North, New Zealand, expressed surprise at the ability of these members of the prosaic cabbage family to easily absorb gold dissolved in ammonium thiocyanate. The team proceeded to demonstrate in lab tests that mustard plants grown in soil containing 4 parts per million (ppm) of gold readily concentrated the metal in their stems and leaves. Brooks and Anderson believed that the process could similarly retrieve not only gold but also other precious metals, such as palladium used to make jewellery. The New Zealand scientists believed that this could become financially worthwhile when gold reached $300 an ounce. According to the report in Nature, about 17 micrograms of dry-weight gold was extracted from the plant ash of each crop harvested. But before you start buying up all the mustard seed you can lay hands upon and plant the backyard, consider this: Not only must the plants be reduced to ash, but the ash itself must then be further exposed to very high temperatures. Further treatment of the resulting residue is then necessary, using exceedingly toxic substances likely to attract the attention of inquisitive neighbours to say nothing of anti-terrorist authorities. So perhaps Brassica juncea is not such a great idea. How about a handy tree then? According to one website, claims have been made that there is enough gold found in a large tree trunk to create a button of gold once the tree has been reduced to ashes, and the gold content has been removed chemically from the ash. Sorry, but think again. Professor Brooks established the catch: Sure, plants can absorb gold from the ground, as long as soil with a rich enough supply of ore can be found.